As the oil price rises rapidly, the cost of vehicle and motorcycle transport is increased. By contrast, using bicycles addresses low-cost transport, saves money, and improves health and environmental protection. As a result, demand for bicycles has increased constantly in recent years and bicycles become the most popular means of transport.
However, bicycle needs not to be registered as vehicle does, and bicycle is much lighter than vehicle. Hence, the bicycle is more likely to be stolen and is unlikely to be found. For improving these drawbacks, many kinds of foldable bicycle have been developed in prior art to facilitate folding, storing and transporting. For example, the U.S. Pat. No. 7,198,281 disclosed that a foldable bicycle 10 as FIG. lA and 1B shown. To eliminate the description of unnecessary details, only specific embodiment and elements of the prior art is described as follow.
FIG. 1B illustrates the unfolded state of bicycle 10. It substantially comprises a front portion 11 and a rear portion 12 which comprise a wheel 20 respectively. The front portion 11 and the rear portion 12 are pivotally connected by a folding joint 31 and a detachable connecting joint 32. FIG. 1B illustrates the folded state of bicycle 10. Thus it can be seen that the front portion 11 and the rear portion 12 can be folded up by means of the folding joint 31 and the detachable connecting joint 32 for the purpose of saving space. Most prior arts, for instance U.S. Pat. No. 7,198,281 or any similar foldable bicycle, provide a foldable bicycle main body by means of improving the structure of the main body. However, as FIG. 1B shown, in the unfolded state, the wheels 20 of the bicycle are so large that they take up space. Thus, there is still room for improvement in space saving for bicycle storage. In other prior art, there is a foldable bicycle with mini wheels (e.g. wheel diameter is relative small) to saving the space taken by the wheel. But small-diameter wheels may influence the performance of bicycle.
As mentioned above, the prior arts have disclosed the structure of foldable bicycle for the purpose of saving space. But, in the prior art, the wheels are unfoldable and the bicycle cannot save the space taken by the wheels. Furthermore, the size of the wheels may influence the performance of bicycle and the convenience of folding and carrying of bicycle. Such indispensable factor is a dilemma of designing bicycle.